The present invention relates to a liquid-filled type vibration isolator used for a suspension or an engine mount of an automobile and a manufacturing method thereof, particularly to an approximately cylindrical liquid-filled type vibration isolator that isolates a vibration along the axial direction and a manufacturing method thereof.
Background Technology
There has been widely known a liquid-filled type vibration isolator that produces a damping force by a liquid filling inside of the isolator.
For example, in Japanese Patent Publication No.50135/1994, there is disclosed a liquid-filled type vibration isolator inside of which there is provided a pair of liquid chambers communicating with each other through an orifice path. With expansion and contraction of the liquid chamber induced by inputted vibration, the liquid flows in the orifice path to thereby produce the damping force.
The liquid-filled type vibration isolator is provided with an outer cylinder and an inner cylinder concentrically arranged inside the outer cylinder. Between the outer cylinder and the inner cylinder, the first fluid chamber, the second fluid chamber and the orifice path are formed by an approximately annular first rubber member, an approximately annular intermediate rubber member, and an approximately annular second rubber member. The first rubber member connects a first ring secured to an end of the outer cylinder and an outer periphery surface of an end of the inner cylinder. The intermediate rubber member connects a cylindrical first sleeve press fitted onto an outer periphery surface of the outer cylinder to be secured thereto and an orifice ring approximately U-shaped in cross section secured to an inner periphery surface of the outer cylinder. The second rubber member connects a second sleeve press fitted onto the other end of the inner cylinder to be secured thereto and the other end of the outer cylinder.
In thus constituted liquid-filled type vibration isolator, however, three kinds of molding tools are required for performing vulcanization molding of the first rubber member, the intermediate rubber member and the second rubber member, each with a different form. Along with this, the first sleeve and the second sleeve are required to be separately press fitted onto the inner cylinder. Thus, there arises problem of largeness in the number of parts that increases a cost and makes a production process complicated.
The present invention is of a liquid-filled type vibration isolator and a manufacturing method thereof provided for solving the above problem of largeness in the number of parts that increases the cost and makes the production process complicated.
The liquid-filled type vibration isolator according to the present invention is characterized by comprising an inner cylinder, a first ring being approximately L-shaped in cross section, a second ring, an orifice ring arranged between the first ring and the second ring, the orifice ring being approximately U-shaped in cross section, an elastic member of rubber material being cylinder-like, the elastic rubber member having an in-cylinder face integrally combining with the inner cylinder and an out-cylinder face integrally combining with the first ring, the orifice ring, and the second ring, and having a first groove formed on the out-cylinder face between the first ring and the orifice ring, and a second groove formed on the out-cylinder face between the orifice ring and the second ring, and an outer cylinder integrally combined with the first ring and the second ring, the outer cylinder and the first groove forming a first liquid chamber, the outer cylinder and the second groove forming a second liquid chamber, the outer cylinder and the orifice ring further forming an orifice path making the first liquid chamber and the second liquid chamber communicate with each other, and the first liquid chamber, the second liquid chamber and the orifice path being filled with liquid.
Such an integral molding of the inner cylinder, the first ring, the second ring, the orifice ring, and the elastic member reduces the number of parts assembled onto the outer cylinder to decrease the man-hours for assembly, which can lead to reduction in cost and improvement in productivity.
The present invention can provide a structure in which the outer cylinder has a plurality of protrusions on an inside surface thereof, the protrusions being made to engage with at least two of the first groove, the second groove, and the orifice ring to be caught thereby. The structure can be more preferably provided with a structure, in which a certain plurality of the protrusions are arranged in circle on an inside surface of the outer cylinder so that the protrusions are made to engage with one of the first groove, the second groove and the orifice ring to be caught thereby. This allows the first ring, the second ring, and the orifice ring to be easily assembled onto specified positions of the outer cylinder without causing any looseness, and ensures that a desired performance can be provided.
The protrusions are preferably arranged so as not to overlap with one another in an axial direction on an inside surface of the outer cylinder. This allows a plurality of the protrusions to be easily formed on the inner periphery surface of the outer cylinder which protrusions are separated in the axial direction of the outer cylinder and arranged along in the circumferential direction of the outer cylinder.
The liquid-filled type vibration isolator according to the present invention can provide a coating layer integrated with the elastic member in an inner face of the groove around the orifice ring with an inner bottom face opposite to the outer cylinder in the orifice path kept to be formed in a convex face approximately circular-arc-like in cross section.
This can reduce the cross sectional area of the orifice path by the shape of the convex face of the inner bottom face of the orifice path to enable the peak frequency of damping to be reduced. Along with this, change given in the cross sectional shape hardly causes turbulent flow in the orifice path to lessen a pressure loss near the entrance of the orifice path. This effectively increases a loss factor as a liquid-filled type vibration isolator.
In addition, a method of manufacturing a liquid-filled type vibration isolator according to the present invention is characterized by comprising the first step of molding an elastic member of cylinder-like rubber material having an in-cylinder face integrally combined with an inner cylinder and an out-cylinder face integrally combined with a first ring, an orifice ring, and a second ring, the elastic member having a first groove formed on the out-cylinder face between the first ring and the orifice ring, and a second groove formed on the out-cylinder face between the orifice ring and the second ring, the second step of forming a plurality of protrusions on an inner face of an outer cylinder, and the third step of assembling the elastic member and the outer cylinder in liquid. This allows the above-described liquid-filled type vibration isolator to be easily manufactured with less number of parts and less assembling man-hours.
In the above manufacturing method, the first step of molding the elastic member includes setting of the first ring, the orifice ring, the second ring, and the inner cylinder in a molding tool, and injection of the rubber material into the molding tool for integrally molding the elastic member together with these component members.
In addition, the second step of forming the protrusions includes setting of an inner mold inside the outer cylinder, setting of an outer mold around the outer cylinder, and an application of a specified force to the outer mold for forming the protrusions. Moreover, the inner mold is column-shaped with an outer diameter approximately equal to an inner diameter of the outer cylinder and has a plurality of depressions on an outer face thereof, and the outer mold is cylinder-shaped with an inner diameter approximately equal to an outer diameter of the outer cylinder and has a plurality of protrusions at positions corresponding to the respective depressions on the inner mold. This allows the outer cylinder having a plurality of the protrusions on the inner periphery surface to be easily manufactured.
In the above second step, the inner mold is constituted of an upper mold and a lower mold being divided from each other by a stepped parting line comprising line segments along a circumferential direction and line segments along an axial direction, the depressions are arranged on an outer face of the inner mold so as to be positioned on the parting line, and the outer mold is divided at equal intervals into a plurality of parts so that the outer mold can be radially disassembled. This allows the protrusions formed on the inner periphery surface of the outer cylinder to be easily formed on a portion where they are not overlapped with one another in the axial direction of the outer cylinder.
Furthermore, the third step of assembling the elastic member and the outer cylinder includes submergence of the outer cylinder with protrusions, and the elastic member integrally molded with the first ring, the second ring, the office ring and the inner cylinder in liquid, insertion of the elastic member into the outer cylinder, and combination of the outer cylinder with the first ring and the second ring for sealing.
Moreover, the method of manufacturing the liquid-filled type vibration isolator according to the present invention allows, in the first step of molding the elastic member, an inner periphery surface of a projected part of a mold to be subjected to cutting beforehand in concave approximately circular-arc-like in cross section, the projected part being for molding an inner face of a groove around the office ring, and the mold being for integrally molding the elastic member with the inner cylinder, the first ring, the second ring, and the orifice ring. This can make an inner bottom face opposite to the outer cylinder in an orifice path formed in a convex face approximately circular-arc-like in cross section. In addition, by adjusting the height of the convex face by the cutting, the cross sectional area of the orifice path can be adjusted to allow a peak frequency of damping to be adjusted for reduction. Furthermore, the inner periphery surface of the projected part being cut in concave approximately circular-arc-like in cross section allows a coating layer covering the orifice ring to be molded in being well balanced.
The molding tool comprises both of upper and lower molds molding the upper and lower faces of them, respectively, and a radially dividable intermediate mold provided between both of the upper and lower molds for molding outer periphery, the intermediate mold being to be provided with the projected part on an inner periphery thereof for molding the inner face of the groove around the office ring, and the inner periphery surface of the projected part being subjected to cutting in concave approximately circular-arc-like in cross section for making an inner bottom face of an orifice path to be formed in convex approximately circular-arc-like in cross section, the inner bottom face being opposite to the outer cylinder.